An inverse methodology for high-frequency RF coil design for MRI with de-emphasized B1 fields.

An inverse methodology for the design of biologically loaded radio-frequency (RF) coils for magnetic resonance imaging applications is described. Free space time-harmonic electromagnetic Green's functions and de-emphasized B1 target fields are used to calculate the current density on the coil cylinder. In theory, with the B1 field de-emphasized in the middle of the RF transverse plane, the calculated current distribution can generate an internal magnetic field that can reduce the central overemphasis effect caused by field/tissue interactions at high frequencies. The current distribution of a head coil operating at 4 T (170 MHz) is calculated using an inverse methodology with de-emphasized B1 target fields. An in-house finite-difference time-domain routine is employed to evaluate B1 field and signal intensity inside a homogenous cylindrical phantom and then a complete human head model. A comparison with a conventional RF birdcage coil is carried out and demonstrates that this method can help in decreasing the normal bright region caused by field/tissue interactions in head images at 170 MHz and higher field strengths.     

合同能源管理公司引入PMP项目管理模式的探讨

随着节能减排在全国各行业的进一步推进,合同能源管理作为一种全新的节能模式引起重点关注,合同能源管理项目也迅速增多.针对合同能源管理项目的运作模式和特点,合同能源管理公司需要建立一套适应的项目管理模式来进行系统全面高效的项目管理,以提高项目成功的机率.文中针对上述需求,探讨引入PMP项目管理模式.     

基于嵌入式Linux的北斗二代接收机应用开发

基于嵌入式Linux,使用UM220和TE6410开发板,完成了北斗二代接收机的应用开发。通过嵌入式Linux和Qt/E的移植,实现了Qt的GUI界面显示,利用Linux多线程的特点,完整实现了NMEA数据的接收、处理、显示以及可视星的星座图显示,对北斗二代系统终端的开发有一定的借鉴意义。     

Java平台测试策略

本文基于Java卡测试库平台TCK工具,对Java卡测试的关键技术进行了深入分析和研究,提供了拓展Java卡测试案例的一种具体实现.本文详细描述了Java卡测试平台运行的系统架构及工作流程,进行了深入的分析,并讨论了为提高Java卡测试案例的全面性和灵活性所采取的策略.实践结果表明,该测试案例拓展方法可高效灵活地提高Java卡平台测试的质量.     

Beyond 3G移动通信系统的小区搜索算法

本文给出了一种可用于Beyond3G的帧结构,利用在物理帧中添加单载波调制的同步信道的方法来实现快速小区搜索。小区搜索过程主要包括时隙同步、帧同步和小区识别过程。本文通过对小区搜索算法的检测概率和虚警概率进行分析,推导出小区搜索的平均搜索时间来分析设计方案的性能。最后,通过在IMT-2000modelA信道环境下对小区搜索算法的性能进行仿真,验证了设计方案的正确性。     

WDM驱动程序和上层应用程序之间建立通信方法讨论

介绍了在Windows操作系统下,使用WDM(Windows Driver Model)模型进行编程的设备驱动程序和上层应用程序之间相互通信的几种方法,并详细讨论了它们的优缺点及适用范围.     

预测校正型曼Ⅱ码译码器技术研究与实现

文章针对计算机系统中串行总线的通讯,提出并实现了一种预测校正型曼Ⅱ码译码器.以预测校正型方式实现的曼Ⅱ码译码器,极大的提高了总线通讯的可靠性,节省了硬件资源,提高了系统的速度.该译码器已经应用于1553B总线控制器LS-FT33中,至今运行可靠.     

Personal identification using feature and score level fusion of palm- and fingerprints

The ever increasing demand of security has resulted in wide use of Biometric systems. Despite overcoming the traditional verification problems, the unimodal systems suffer from various challenges like intra class variation, noise in the sensor data etc, affecting the system performance. These problems are effectively handled by multimodal systems. In this paper, we present multimodal approach for palm- and fingerprints by feature level and score level fusions (sum and product rules). The proposed multi-modal systems are tested on a developed database consisting of 440 palm- and fingerprints each of 55 individuals. In feature level fusion, directional energy-based feature vectors of palm- and fingerprint identifiers are combined to form joint feature vector that is subsequently used to identify the individual using a distance classifier. In score level fusion, the matching scores of individual classifiers are fused by sum and product rules. Receiver operating characteristics curves are formed for unimodal and multimodal systems. Equal Error Rate (EER) of 0.538% for feature level fusion shows best performance compared to score level fusion of 0.6141 and 0.5482% of sum and product rules, respectively. Multimodal systems, however, significantly outperform unimodal palm- and fingerprints identifiers with EER of 2.822 and 2.553%, respectively.     

Low Complexity Time Domain Interleaved Partitioning Partial Transmit Sequence Scheme for Peak-to-Average Power Ratio Reduction of Orthogonal Frequency Division Multiplexing Systems

As an attractive technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems, time domain interleaved partitioning partial transmit sequence (TD-IP-PTS) scheme uses circular convolution property of discrete Fourier transforms (DFT) so as to need only one inverse fast Fourier transform (IFFT) operation. However, the search and combination of phase factors still need higher computational complexity. In order to improve the problem, this paper detailedly analyzes the independence of phase factor vectors and optimizes the phase factor vectors in TD-IP-PTS. Furthermore, we find the characteristic of combination of phase factors and propose three methods respectively based on storage-unit, pipeline and select-path to implement the combination of phase factors in TD-IP-PTS. The simulation results show that TD-IP-PTS using independent and effective phase factor vectors has better PAPR performance and lower complexity than traditional IP-PTS. Moreover, among three proposed methods for combination of phase factors, the method based on select-path requires the least registers and delay time. This method is the most promising in practical applications.     

PCC策略控制机制研究及在网络中的部署

PCC (Policy and Charging Control)是3GPP定义的动态策略和计费控制的框架方案,旨在为用户提供差异化的服务,提供用户业务流承载资源保障以及流计费策略.本文介绍了PCC机制的基本架构及相应策略规则,对PCC在现网中的部署进行了探讨,并针对核心网未来的发展趋势给出EPC架构下PCC的部署建议...